I'm confused

From Stumbling and Mumbling: "The correlation between IQ and earnings is low. This review (pdf) of the literature estimated that a on standard deviation difference in cognitive skills is associated with only a 10% difference in wages."

From Magan's Miscellany: "Charles Murray's Income Inequality and IQ says that the top quintile in IQ earns 4.8 times that of the bottom quintile."